Ruangtrakoon, Natthawut

Preferred name

Main Affiliation

School of Engineering

natthawut.ru@kmitl.ac.th

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Performance investigation for CRMC and CPM ejectors applied in refrigeration under equivalent ejector geometry by CFD simulation
(2022-11-01)
Bumrungthaichaichan, Eakarach
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Ruangtrakoon, Natthawut
;
Thongtip, Tongchana
In this paper, one of the remaining questions for ejector design, “Does the constant rate of momentum change (CRMC) ejector provide better performance than the constant pressure mixing (CPM) ejector under identical ejector area ratio, ejector length, and operating conditions?”, has been answered. Two steam ejector designs operating with the various boiler and evaporator temperatures were simulated by the SST k-omega turbulence model. The present computational fluid dynamics (CFD) model produced a reasonable agreement with our previous published experimental data. The upstream operating conditions were simultaneously considered to assess the better performance ejector design with the help of the primary expansion coefficient. The predicted results revealed that the CRMC ejector showed an advantage in entrainment ratio and a disadvantage in critical condenser pressure. However, the ejector efficiency comparison confirmed that the CRMC ejector design provided better performance than the CPM ejector design for a primary expansion coefficient greater than unity. The maximum percentage improvement of ejector efficiency was 32.418%.
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Experimental investigation of small radial-flow expander in micro-scale organic rankine cycle powered by low temperature heat source
(2025-07-01)
Thongtip, Tongchana
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Singmai, Wichean
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Jamsawang, Suparat
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Ruangtrakoon, Natthawut
;
Sutthivirode, Kittiwoot
The in-house development of a radial-flow expander is proposed which aims to investigate the performance under various working conditions. The radial-flow expander is installed into a micro-scale Organic Rankine Cycle (ORC) test bench. An experimental investigation is also proposed in an attempt to discuss the operating characteristics and the system performance. The mathematical model for designing the expander is proposed and the validations of the designed performance parameters with the tested parameters is also implemented to ensure that the radial-flow expander is developed correctly. The operating characteristics of the vapour-generator with variations in the working fluid flow rate which reflects the best heat transfer performance is also a main focus. This is significant for producing the thermodynamic state of the vapour at the outlet of the vapour-generator. The overall heat transfer coefficient (U<inf>ref</inf>) based on the flow boiling at the vapour-generator is determined. The maximum shaft power and maximum thermal efficiency are determined under various working conditions. This paper also provides evidence of the ORC system operating with a low temperature heat source (range 80–90 °C). The thermal efficiency is as high as 2.5–3.5 % depending on the the working conditions. The overall heat transfer coefficient for the flow boiling at the vapour generator is 280 to 700 W/m<sup>2</sup>.K.
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Thermo-Economic Assessment of the Organic Rankine Cycle Combined with an Ejector Cooling Cycle Driven by Low-Grade Waste Heat
(2025-12-01)
Singmai, Wichean
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Janpla, Pichet
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Sutthivirode, Kittiwoot
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Thongtip, Tongchana
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Ruangtrakoon, Natthawut
This paper proposes an energy, exergy, economic, and exergoeconomic (4E) analysis of an Organic Rankine Cycle (ORC) enhanced by an ejector refrigeration system. The two systems are combined via an intercooler, where the unwanted heat is transferred to the ejector cooling loop. The major objective is to reduce the discharge pressure of the expander so that higher power is achieved. However, the combined system requires more equipment and energy input, and, hence, 4E analysis is an efficient tool for assessing the feasibility of it in practical use based on a comprehensive analysis. This study aims to provide a systematic 4E-based evaluation of an ORC integrated with an ejector cooling cycle under realistic tropical conditions. The innovation of this work lies in combining unified thermodynamic, economic, and exergoeconomic assessments to quantify both performance enhancement and cost interactions attributable to condenser-side cooling. The findings offer significant insights into the dominant thermal–economic trade-offs, identify key cost drivers within the ORC + ECC configuration, and highlight operating conditions that maximize the power output and minimize the electricity generation cost. These results contribute practical guidelines for improving the feasibility and deployment of ORC–ejector systems for low-grade heat recovery applications. A theoretical model is formulated to examine both energy and exergy performance indicators together with key economic metrics. Parametric investigations are conducted to investigate the effects of the intercooler temperature (16–22 °C) and generator temperature (70–85 °C) on overall system performance. It is found that the integration of an ejector cooling cycle (ORC + ECC) can significantly enhance the thermo-economic potential of waste heat power generation systems compared to a standard ORC, from both exergoeconomic and LCOE perspectives. The exergoeconomic analysis identified that, while the expander dominates the cost of the standard ORC, the condenser and cooling tower become critical components of the ORC + ECC due to their high exergy-destruction costs. At the system level, the LCOE results confirm that the ORC + ECC can achieve 37–38% lower electricity generation costs compared to the standard ORC.
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Real air-conditioning performance of ejector refrigerator based air-conditioner powered by low temperature heat source
(2021-02-01)
Thongtip, Tongchana
;
Ruangtrakoon, Natthawut
In this present work, the air-conditioning test performance of an ejector refrigerator-based air-conditioner (ERAC) was proposed. The ERAC was operated as the water chiller to produce the cooling load up to 4.5 kW. The chilled water temperature was later supplied to the fan-coil unit for producing the thermal comfort condition. The cooling water used to cool the condenser was achieved from the cooling tower which was operated under the hot and humid ambient. This is to demonstrate the feasibility of using the ERAC in real working conditions. The cooling load supplied to the air-conditioned space was applied by the air heater. The ERAC could efficiently be operated to produce the thermal comfort condition which was driven by the hot water temperature (T<inf>hot</inf> ) of 90–98<sup>◦</sup> C. The system performance could vary with the heat source temperatures, cooling load, primary nozzle, and air-conditioned space temperature. The optimal performance was determined when varying the T<inf>hot</inf>, and, hence, the optimal T<inf>hot</inf> was indicated. The optimal T<inf>hot</inf> varied significantly with variations in the working condition. The test results demonstrated high potential to further using the ejector refrigeration system in the actual air conditioning application.
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Comparison of traditional and CRMC ejector performance used in a steam ejector refrigeration
(2017-01-01)
Kitrattana, Borirak
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Aphornratana, Satha
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Thongtip, Tongchana
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Ruangtrakoon, Natthawut
In this paper, performance of a steam ejector designed based on the constant rate of momentum change (CRMC) and traditional ejector were tested in an attempt to compare its performance. Three different ejectors were designed and constructed; traditional ejector with throat diameter of 19 mm, traditional ejector with throat diameter of 13.4 mm, and CRMC ejector with throat diameter of 13.4 mm. They were designed to be easily equipped with the 1kW experimental ejector refrigerator. The boiler saturation pressure was varied from 130°C to 140°. The evaporator saturation temperature were fixed at 7.5°C. The result show that at the same operating condition and the same ejector area ratio (the area ratio of nozzle throat to ejector throat), CRMC ejector provided higher entrainment ratio than the traditional ejectors while the critical condenser pressure remain the same.
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An experimental investigation to determine the optimal heat source temperature for R141b ejector operation in refrigeration cycle
(2020-04-01)
Ruangtrakoon, Natthawut
;
Thongtip, Tongchana
This paper provides an experimental investigation of an R141b ejector refrigeration system which concentrates on the effect of the driving generator temperature on the ejector performance under various working conditions. The experimental ejector refrigerator working with R141b was designed and built for investigation. The generator temperature was varied to determine the optimal generator temperature. The working generator temperature was varied between 80 and 105 °C. The evaporator temperature was ranged from 6 to 14 °C. Three primary nozzles were used to investigate the effect of the ejector area ratio to the optimal performance. The condenser saturation temperature was ranged from 28 to 34 °C. It was found that the optimal generator temperature varied with the change in the working conditions and primary nozzle used. With variation in the evaporator temperature, the upstream pressure ratio was initially introduced and its impact on the optimal operation was later discussed. This upstream pressure ratio strongly influenced the optimal operation at relatively high evaporator temperature, and hence, the proper value was determined for this present work. In addition, the proper ejector area ratio for working condition consistent with this present work was determined. The results also demonstrated the feasibility of using an ejector refrigerator with a relatively low generator temperature while rejecting unwanted heat at relatively high condensation temperature.

Ruangtrakoon, Natthawut

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